<!DOCTYPE html>
	<html>
	<head>
		<meta charset="utf-8"/>
		<title>作业2</title>
		<style>
			.form{
				border:1px solid #ccc;
				width:100px;
				height:30px;
				text-align:center;
				line-height:30px;
				margin:20px auto;
			}
			.form:hover{background:#ccc;}
			.form ul{
				padding-left:0;
				margin:0 0 0 -1px;
				display:none;
				list-style-type:none;	
				width: 100%;			
			}
			.form ul li{				
				border:1px solid #ccc;
				width: 100%;		
			}
			.form ul li:hover{background:#ccc; color:#fff;}
			.form:hover ul{display:block;}
		</style>
	</head>
	<body>
		<div class="form">无序列表
			<ul>
				<li>无序1</li>
				<li>无序1</li>
				<li>无序1</li>
				<li>无序1</li>
			</ul>
		</div>
	</body>
</html>